I'm currently planning on building a boat ladder for my dogs (two
dogs, ~80 lbs each) and was wondering if anyone has some suggestions.
I was thinking about using PVC to build the ladder frame, and then
strapping sheets of fiberglass or something water-friendly to the PVC
frame. I figure some of you woodworkers (thus the post to
rec.woodworking) might have some tips on design and/or materials,
because obviously you can't just build everything out of wood all the
time, right?

My current design would be a 2-step ladder, again with a frame built
out of PVC. The frame would attach to the boat with a simple rope and
hook assembly to the back of the boat. I would like the fiberglass
sheets to be detachable from the frame fairly easily so that the
design is friendly for storage. Another concern is that the bottom
step needs to be submerged underwater, i.e. not floating. The
PVC/fiberglass combo is the best I can come up with, but perhaps
someone has a better suggestion?

Disclaimers:

(1) I know you can buy ladders like this, but from what I've seen,
they're aren't many options, and they're typically very expensive. I
think I can build something that suits my needs for considerably less
money.

(2) I know some people have taught their dogs to climb up their
foldout ladders. I don't see how this is possible with my dogs, the
rungs on the ladder are way too narrow for their paws.

(3) I know I cross-posted this to rec.woodworking, but I also know the
people in that newsgroup are pretty good with their hands and might
have some tips on my assembly. If someone can recommend a better
newsgroup for this post, please let me know, as my intent isn't to
post this somewhere where it's frowned upon.

Thanks,
Dustin